Variable condenser with trimmer



Jan. 4, 1949.

Filed Jan 25, 1945 S. R. MONTCALM VARIABLE CONDENSER WITH TRIMMER 2 Sheets-Sheet l HUIIIIIHF H I IIII NVENTOR SURRIUS RECTOR MONTCALM ATTORNm Jan. 4, 1949. s. R. MoNTcALM 2,458,187

VARIABLE CONDENSER WITH TRIMMER Filed Jan. 25, 1945 2 Sheets-Sheet 2 FIG. 4

1N VEN TOR.

SURRIUS RECTOR MONTCALM BY CM@ AT ORNEY Patented Jan. 4, 1949 VARIABLE CONDENSER WITH TRIMIYIER Surrius Rector Montcalm, Boonton, N. J., assigner to Ferris Instrument Laboratories, Boonton, N. J., a. corporation of New Jersey Application January 25, 1945, Serial No. 574,533

2 Claims. 1

My present invention broadly relates to a mechanical device adapted for being associated with an electrical device for modifying its electrical effects, and particularly to such a device having one or more of its elements adjustable in positioning with respect to a xed element of the same and/or an element or elements associated therewith.

An object of my present invention is to have the positioning of the element or elements of the device involved remain substantially fixed following an adjusting operation or adjusting operations.

Another object of my present invention is to have the adjustability of the element or elements of the device involved include minute or iine degrees of adjustment.

And one specic object of my present invention is to make the mechanical device involved especially adaptable for use as a so-called trimmer for an electrical variable capacitance device and particularly so where the variable capacitance device is the principal tuning element in a tunable electrical circuit vthat is required to closely follow some predetermined law in respective responsivenesses to operating potentials of electrical alternating currents brought to bear upon the circuit involved.

It is considered most likely that other objects accomplishable by the utilization of my present invention will be quite readily apparent to those familiar with the art involved from the following more or less in detail description of it with the aid of the several figures of the accompanying drawings in which figures like reference symbols refer to parts like in kind or equivalent in function.

Referring-to the drawing, briefly stated Fig. 1 illustrates in elevation a side view of the mechanical device involved. Fig. 2 illustrates in elevation a cross-sectional end view of the mechanical device involved on the line ZZ of Fig. l. Fig. 3 illustrates in elevation an end view of an electrical variable capacitance device dually equipped with the mechanical device involved for so-called trimming purposes. And Fig. 4 illustrates a cross-sectional elevation side view of a portion of what is illustrated by Fig. 3 taken on line XX of Fig. 3.

Referring in detail to Fig. 1, the element B indicates a base comprising a bar rectangular in .cross-section (see Fig. 2), preferably of metal of high electrical conductivity, bored to receive the screws l, 2 and 3 for holding it in place, and

further bored and threaded to receive the indicated screw members II, 5, 6, 1, 8 and 8. The element B indicates another base inserted between base B and its mounting place, and referring to Figs. 1 and 2 the elements I3, I4, I5, I6, II and I8 illustrate leaf-like members integral with or effectively bound to base B; all, including base B', being preferably of metal highly conductive of electricity.

Referring in detail to Fig. 2, the back side of base B is indicated as bored at I I into the boring I0 receiving the threaded screw 9 which is indicated as having a tapered end contactable with an indicated metal ball I2 located in the boring II that is contactable with the leaf-like element I3.; from all of which it is altogether obvious that the more the ball I2 is pushed outwardly by the tapered screw member 9 as it is moved downward by screwing downward action the farther away from the back side of base B is the leaf-like element I3 moved by the forcefully pressing thereon ball I2, and that by its springy action the leaflike element I3 returns to its neutral position as upward movement of the screw member 9 permits the ball I2 to recede inwardly in the boring II under the spring-like action of the leaf-like element I3.

Referring again to Fig. 1, it is obvious that if any additional leaf-like elements other than I3 are needed, they may be individually and respectively treated for selective positioning with respect to the back side of base B in the same way as that illustrated with respect to leaf-like element I3 by Fig. 2. It so happens that in special work I have done with the aid of my present invention which will be outlined later on I found it necessary to add the five leaf-like elements I4, I5, I6, II and IB as shown by Fig. 1.

Referring to Fig. 3, it illustrates in elevation an end view of a decidedly unique electrical variable capacitance device of a somewhat modified form over that illustrated in an application of Harold E. Barnes Serial No. 542,192, led June 26, 1944, in that I show an extension integral with one end of the single rotor R of his device. The device of his application accordingly comprises two massive stators SI and S2 having massive terminals TI and T2, respectively, having interposed between the respective sloping sides of the said stators a massive rotor R having corresponding sloping sides to which I have added the indicated one end extension RE. The indicated element B shown as being on the in-view end of each of the stators indicates that each of these stators is equipped with a device representing my present invention, but to avoid unnecessary dupliconsidered to be included in whole or in part as the circumstances may require.

Referring to Fig. 4, it being indicated by the line XX' as a cross-sectional'in elevation side view of Fig. 3 in the plane of the said line, it

' shows more in full the extension I have made to the rotor R and that the supporting arm A is pivoted at P to provide for the necessary rotary movement required to obtain the necessary variations in capacitance. Also, that the element B is xedly held in place by the screws I, 2 and 3 being screwed into threaded borings in stator Si and that the leaf-like elements I3 to I8, inclusive (or any number required), coextend with the extension RE; however, it is clearly obvious that the relative coextension may be varied over very wide ranges depending upon what is to be accomplished.

Assuming that the stators, the terminals, the rotor and the rotor extension are made of material highly conductive of electricity as is always the case in high grade 'capacitance devices, for any given active capacitance area the amount of capacitance varies inversely with the distance of separation and directly as the dielectric constant of the interposed dielectric which in the instant case is air Ahaving the low dielectric constant of 1. In resonantly dealing with electrical alternating currents of high, very high and ultra high frequencies which occur in a range such as from to 250 megacycles, it is axiomatic-with respect to the electrical circuits involved that .as the frequencies of operation increase lower and lower values of inductance and capacitance must be brought to bear, and so much so that if the inherent inductance of the capacitance device is not somewhere near the lowest possible even with air as a dielectric the capacitance cannot be made low enough to have a combination of inductance and capacitance such that resonating at the very high and ultra high frequencies will be possible of accomplishment. Because of the exceptional massive nature of the respective elements of the capacitance device illustrated in Figs. 3 and 4 I have found that the inherent inductance therein is so low that even at 250 megacycles a little external inductance can be added without exceeding the very low inductance that is required dueto the lowness of the obtainable capacitance being also quite limited.

With this special capacitance device I have cooperatively worked on building a special signal generator capable of generating in a single unit with a single electronic generator electrical alternating currents covering in six bands from 20 to 250 megacycles in which it was required to have three cascaded tunable electrical circuits operate in resonance with each other throughout the entire band of 20 to 250 megacycles, and

by using the mechanical device of my present invention for trimming the said capacitance device in the manner shown by Figs. 3 and 4 in the first two circuits of the cascade and a special trimmer controllable from the panel in the third circuitof the cascade undisputed commercially acceptable success in the so-called tracking or lining up of the circuits involved was thereby obtained.

In thepartlcular device a great amount of stage-by-stage and over-all shielding is necessary, so that in order for the tracking to be satisfactory inthe finished product the trimming must be carried out with most of the shielding in place. To make this possible, for those of the trimming screws 4, 5, 6, 1, 8 and 9 need-ed in-line holes are made in the shielding covering the same through which the necessary tool for trimming can be inserted. The said holes can, of course, be plugged up with shielding material after trimming is completed if the service forwhich the finished product is destined requires this refinement step.

Referring to the details with respect thereto shown by Figs. 3 and 4, it is-particularly apparent therefrom that as rotor R moves its added extension RE, andthe additional capacitance for regulating the overall capacitance values consequently becomes less and less, the number of trimming elements eiectively participating in regulating the total capacitance values becomes less and less to thereby make it easier to adjust to the proper trimming at the corresponding more critical to adjustment higher frequencies.

While I have described my present invention in certain confined respects, it is apparent that modifications may be made, and that no limitations are intended other than those imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In an electrical variable capacitance device adapted for creating the major parts of the variable capacitive reactances in electrical circuits designed to selectively resonate to electrical alternating currents of variable frequencies ranging as high as 250 megacycles and m-eans associated therewith for causing the selective resonating at the desired frequencies to be eiTec-,

tively accomplished: the combination of two single sloping side stators and a ro'tor having two correspondingly sloping sides variably interposed therebetween, all of material highly conductive of electricity and so massive in all relevant directions that the inherent reactive inductance set up thereby to electrical alternating currents of frequencies even as high as the order of 250 megacycles is still low enough to permit of using some inductance externally thereof in the circuits in which connected; an otherwise nonessential extension of the body of said rotor beyond and partially overlapping of said stators in maintained massive form; and means for causing any circuit in which said variable capacitance device is located to eiectively resonate at all of the great many frequencies involved at predetermined settings of said rotorirrespective of said circuit per se not being otherwise adapted for so resonating, comprising a separate base member mounted on a portion of' each of said stators nonoverlapped by said extension, said base member having a fiat side facing said extension and a at base substantially at a right angle to said' at side and including a plurality of threaded holes therein; separate holes leading from said flat side to each of said threaded holes at a material distance from said iiat base in each case;

.separate leaf like elements extending from said diameter sumciently greater than its holes depth that in response to a downward movement of the tapered point of its corresponding screw member it causes its corresponding leaf-like element to alter its position with respect to its neutral position; whereby the different positions given such of said leaf-like elements as may be required will change the capacitance of said ca` pacitance device enough in each case to cause the desired effective resonating of the circuit involved without increasing the overall inherent inductance consequently encountered in operations at frequencies of the order of 250 megacycles enough to render continued resonating at such frequencies impossible of attainment due to the overall inductances involved being raised too much for supporting resonance with the consequently raised overall capacitances involved, respectively.

2. The combination of claim 1 in which the respective base members are so mounted on the respective stators that as the rotor moves away 20 Number 6 from the stators to reduce the capacitance of the variable capacitance device the movement of the rotor extension is away from the leaflike elements in increasing numbers, to thereby mak-e the variable capacitance device progressively less affected by the adjustments made for the lower frequencies.

SURRIUS RECTOR MONTCALM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Schellenbach Apr. 8, 1924 Sagle Aug. 25, 1936 FOREIGN PATENTS Country Date Italy Jan. 30, 1940 Number 

